(1) hGH batches of 150 mg were plasmin digested and fractionated to yield hGH isohormones D and E. These were bioassayed in the rat and found to be bioactivated. The bioactivity was found to be stable on storage in liquid nitrogen. Stored batches are being accumulated for testing in patients. (2) Adenylate cyclase and (3) insulin receptors have physically characterized with maintenance of activity. (4) Characterization of progesterone receptors from chick retina is in progress.